A systematic investigation on the hybrid Darrieus-Savonius vertical axis wind turbine aerodynamic performance and self-starting capability improvement by installing a curtain

The Darrieus vertical axis wind turbine is categorized as a lift-based power generation turbomachine. However, the challenge of self-starting capability poses a potential obstacle for this turbine. This study addressed this issue by incorporating a Savonius rotor and introducing a Darrieus-Savonius hybrid rotor to enhance the aerodynamic performance and self-starting capability. The results demonstrated a substantial increase in power coefficient by 64% at tip speed ratio (TSR) = 1.4. Furthermore, the curtain installation was investigated as a mechanism to improve rotor performance. The findings indicated that the multiplication of a curtain enhanced the self-starting capability by controlling the positive pressure gradient on the suction and pressure sides of the rotor blades. Notably, considering the flow physics and rotor efficiency in the presence of the curtain with walls featuring different angles, it was established that the optimal angles for the upper and lower walls are 20° and 45°, respectively. This configuration led to a 35% increase in rotor efficiency compared to the solo hybrid rotor. The hybrid rotor demonstrated superior performance within the low-TSR range values, while the Darrieus control case exhibited better efficiency in the high-TSR range. Despite the enhancement in performance attributed to the curtain installation, the high-TSR range still lagged behind the Darrieus control case.